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Date: Thu, 16 Aug 2012 15:53:37 +0300 From: "Michael S. Tsirkin" <mst@...hat.com> To: Alex Williamson <alex.williamson@...hat.com> Cc: avi@...hat.com, gleb@...hat.com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v8 0/6] kvm: level irqfd support On Thu, Aug 16, 2012 at 06:34:52AM -0600, Alex Williamson wrote: > > > > So I'm inclined to say source IDs are a requirement for shared > > > > interrupts. > > > > > > Can yo show a specific example that breaks? > > > I don't think it can exist. > > > > Only the edge vs level interaction if we define the policy above for > > de-assert. > > Hmm, there is still a race w/ level. If we have a number of > level-deassert-irqfds making use of the same gsi and sourceid and we > individually de-assert and notify, a re-assert could get lost if it > happens before all of the de-asserts have finished. > We either need > separate sourceids or we need to do a single de-assert followed by > multiple notifies. Right? Thanks, > > Alex Good catch, I agree, we need a single deassert. I think I see how to implement this without reference counting and stuff. So we chain all auto-deassert irqfds for a given GSI together, and have a single ack notifier. When list becomes empty, remove the ack notifier. It's actually a good thing to do anyway, too many ack notifiers would slow unrelated GSIs down. -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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